I've had the exact opposite experience. V5 has been the best performing version for me, and I've been using since inception.
Looking forward to six. I took advantage of the buy 5 at amazon for $40, get a $20 discount, and free upgrade to six option instead of paying the $40 upgrade. Also discovered that if I use one of my many v3 license keys, I get another $20 discount, meaning I upgraded to v6 for free (and got a printed manual in the deal). Not too shabby.